Recent content by Doug_West

z=f(g(x,y)), where g(x,y)=x^2+y^2. Now what does the chain rule tell you about, say ∂z/∂x?

haha yep :D, thanks for the help.

evaluating pt 0,0 I get D<0 where D= -1 and fxx(0,0) = 0, so then this is a saddle point. However is it a saddle point because D<0 or because fxx = 0?

yep those two pts are x=0, y=0 and x=1/6 y=1/12

Homework Statement Find and classify all relative extrema and saddle points of the function f(x; y) = xy - x^3 - y^2. Homework Equations D = fxx *fyy -fxy^2 The Attempt at a Solution I got D < 0 where D = -1 and fxx = 0, when x=0 and y=0. However I am unsure as to the conclusion I should...

0! Thanks for the help. Doug.

f'(g(x,y)))*2

would it be f'(g(x,y))*1?

Homework Statement Let f be a differentiable function of one variable, and let z = f(x + 2y). Show that 2∂z/∂x − ∂z/∂y = 0 Homework Equations Multi-variable chain rule The Attempt at a Solution I have no idea where to start with this, any advice would be greatly appreciated...